Variability of area measurements obtained with different intravascular ultrasound catheter systems: Impact on clinical trials and a method for accurate calibration

Background. Atherosclerotic plaque burden is the major end point in ongoing progression trials. Intravascular ultrasound allows precise measurements of coronary artery dimensions. However, the variability of measurements among different catheter systems is incompletely characterized. Methods: Intravascular ultrasound imaging was performed in a cylindric phantom with 5 sections of different, known, cross-sectional area ranging from 3.24 to 27.99 mm(2). A total of 3637 measurements with different catheter systems (Atlantis SR and Ultracross, Scimed/Boston Scientific; and Invision and Avanar, joined) were performed. Measurements were divided into model building and validation datasets. For each catheter, calibration models were developed. Results: Overestimation and underestimation of the true cross-sectional area of up to 18% was observed with different catheter systems. Calibration equations for the different systems could be developed that predicted the true diameter and area with high statistical precision (adjusted R-2>0.99). Conclusions. Area measurements vary among different intravascular ultrasound catheter systems. Calibration equations can correct for these differences and allow the comparison of measurements among catheters.